1. Field of The Invention
The present invention relates generally to a method and system for controlling a gas system having a plurality of control modes. More specifically, the invention relates to a method and system for controlling a gas system for use in a semiconductor production process.
2. Related Background Art
In a typical production process in a semiconductor equipment, there is widely adopted a method for cleaning an object to be treated (which will be hereinafter referred to as a "wafer or the like"), such as a semiconductor wafer and a glass substrate for a LCD, by subsequently dipping the wafer or the like in a treatment solution, such as a chemical or a rinsing solution (a cleaning solution), which is stored in a treatment bath. In such a cleaning treatment, a drying treatment for removing the moisture content of the wafer or the like to dry the wafer or the like is carried out by bringing the surface of the wafer or the like, which has been cleaned, with a dry gas of vapor of a volatile organic solvent, such as isopropyl alcohol (IPA), to condense or absorb the vapor of the dry gas.
A conventional drying system of this type comprises: a supply part for supplying a carrier gas, e.g., an inert gas, such as nitrogen (N.sub.2); a vapor generator for heating a dry gas, e.g., isopropyl alcohol (IPA), to generate vapor; a supply line for supplying vapor generated by the vapor generator, i.e., the dry gas, to a drying chamber via a shut-off valve; and a heater for heating the supply line. Therefore, since it is important to control the temperature of N.sub.2 gas and the dry gas, which are used for the drying treatment, the temperatures of heaters provided in a N.sub.2 gas supply line, a dry gas supply line and a vapor generator are conventionally controlled.
In a semiconductor production process, a dry etching technique is essential in order to form a fine pattern in a wafer or the like. The dry etching is designed to produce plasmas with a reactive gas in vacuum, to each various materials on a wafer or the like with ions, neutral radicals, atoms or molecules in the produced plasmas. In the dry etching, various gases are used in accordance with the kind of etching materials.
Typically, in an etching system of this type, a container having a closed treatment chamber has an etching gas introducing portion, and an evacuation port for evacuating the interior of the treatment chamber to a predetermined pressure-reduced atmosphere (vacuum). In addition, one of flat plate electrodes, which face each other in the treatment chamber and which also serve as susceptors, is connected to a high-frequency power supply, and the other flat plate electrode is grounded to the container. While the interior of the treatment chamber is evacuated to a predetermined pressure-reduced atmosphere in accordance with the kinds of materials to be etched and reactive gases to be used, a high-frequency power is applied between both electrodes to produce a plasma discharge to etch the wafer or the like with ions, electrons and neutral active species in the produced plasmas. Therefore, since it is important to control the pressure in a treatment chamber at a predetermined pressure-reduced atmosphere in an etching treatment, a pressure regulating means is conventionally provided in an exhaust line connected to an evacuation port, to control the pressure in a treatment chamber.
However, such conventional drying and etching treatments are not designed to change a control parameter every kind and supply condition of gases to carry out the temperature and pressure controls.
Therefore, although there is no problem when a reduced thermal or pressure loaded condition is controlled by using a control parameter for a severe thermal or pressure loaded condition, there is a problem in that control is failed immediately after the reverse situation occurs. In this case, although only the level of load is not so great matter, there is a disadvantage in that it is not basically possible to use a common control parameter between quite different loaded conditions.